Due to the recent heightening need in weight saving, magnesium alloy (or Mg alloy), which is more lightweight than aluminum alloy is, has been gathering attention. Magnesium alloy is about to be used widely for material for automobile, and the like, in addition to material for air craft, because it is the lightest in practical metals. A member comprising an Mg alloy (or Mg-alloy member) is lightweight, and is good in terms of functionality. Moreover, since using an Mg-alloy member leads to making vehicle, and so forth, lightweight, it is possible to intend energy saving.
In reality, however, in a case where an Mg-alloy member is utilized in vehicle, and the like, it is often the case that it has been required to have high-temperature characteristics, such as the heat conductivity, heat-resistance strength and creeping properties, that are suitable for employment in high-temperature environments. Although it is often the case that AZ91D, and so forth, have been used in common Mg-alloy members, such Mg-alloy members are not suitable for employment in high-temperature atmospheres because the creep strengths have been very low. Hence, a variety of Mg alloys whose high-temperature characteristics are improved have been proposed in the following: Japanese Unexamined Patent Publication (KOKAI) Gazette No. 6-279,906; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2000-319,744; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2001-316,753; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2002-327,231; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2004-162,090; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2004-232,060; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2005-113,260; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2006-291,327; Japanese Unexamined Patent Publication (KOKAI) Gazette No. 2007-70,688, and so on.